Patent GB-1389678-A (GB)
Title: Binding tapes
IPC: H01B17/56
Filed: 1972-12-11
Abstract: 1389678 Coated ribbon WESTINGHOUSE ELECTRIC CORP 11 Dec 1972 [22 Dec 1971] 57003/72 Heading B2E A binding tape for wrapping conductors prior to impregnation with a solventless resin comprises a woven ribbon having glass fibres in the fill direction and flexible thermallystable fibres possessing an elongation of at least 2% in the warp direction, the ribbon being coated with a dry resin composition cured beyond the B stage and capable of being swollen by said solventless impregnating resin, and the tape having a roughtextured surface. As shown in the drawing copper wires 1 are separated by insulation 2 wrapped with an insulation tape such as mica tape 3. A tape 4 is wound over the mica insulation forming laps 5. Tape 4 consists of glass fibres 6 in the fill direction and a flexible fibre 7 in the warp direction. A swellable resin 8 coats the fibres to form hills 9 and valleys 10 in the tape. Preferred flexible fibres are polyethylene terephthalate. Other fibres mentioned are polyamide-imide, nylon, polyacrylonitrile fibres. Preferred swellable resins are polyester resins. The preferred resin composition comprises one part by weight of alkyd polyester prepared from 15-30% of the saturated trihydric aliphatic organic compound having 3-7 carbon atoms, preferably glycerol, 15-25% of at least one low molecular weight aromatic compound containing hydroxyl and carboxyl groups, such as salicylic acid, 25-40% of a drying oil such as dehydrated castor oil, and 25- 40% of an aromatic dicarboxylic acid having 8-12 carbon atoms such as terephthalic acid, up to 0.08 parts by weight anti-oxidant, preferably polymerised trimethyl dihydroquinoline, up to 0.6 parts by weight epoxy resin having an epoxy equivalent weight of 65-6000, and up to 0.35 parts by weight thermosetting formaldehyde resin, preferably a melamine formaldehyde resin. Other resins mentioned are phenolic novolak epoxies, cresylic novolak epoxies, acrylics, phenolics, oil-modified phenolics and polyamide-imides. Mixtures of curable resins may also be used. A swellable resin composition may be prepared from 1 parts curable resin, 0.03-1.1 parts filler, preferably talc, silica, powdered mica, calcium carbonate, calcium silicate or mixtures thereof, and 0.014-0.26 parts swell accelerator, i.e. a low molecular weight material with hydroxyl, carboxyl, oxirane, and/or amino functional groups, preferably castor oil. The swellable resin composition may be applied to the ribbon from a solvent or suspending agent by immersion. Examples of solventless electrical impregnating resins are styrenepolyester, epoxy, epoxy-anhydride, styreneepoxy-anhydride, silicone and polyurethane resins. In a typical example a woven ribbon having glass fibres in the fill direction and polyethylene terephthalate fibres in the warp direction is immersed in a swellable resin composition. The swellable resin composition comprised 1100 parts polyester resin, 400 parts talc, 25 parts silicon dioxide, 60 parts 50% solution in xylene of polymerised trimethyl dihydroquinoline, 75 parts castor oil, 275 parts toluene, 87.5 parts diglycidyl ether prepared from epichlorohydrin and bisphenol A, 282.5 parts of a solution in methylethyl ketone of a diglycidyl ether prepared from epichlorohydrin of bisphenol A, 200 parts of a 65% solution in xylene of butylated melamineformaldehyde resin. Copper tubes wrapped with half inch polyethylene terephthalatebacked mica tape and then 1/4 lapped with the above tape and immersed in a styrenepolyester resin. The tubes were then cured.